Martin Spott wrote:
Pigeon wrote:
FG's scenery (0.9.10) is generated using the landmass, and as you
can see from the above link, there are rather big differences between
the landmass and the coastline/swbd, especially with the main island
(the one that looks like a frog).
This is a major difficulty that has been discussed several years now -
the discussion had started long before SWBD was available.
I won't be able to deliver a satisfying response to this question, but
at least I might make one point clear:
- VMAP0 'landmass' focuses on political boundaries and may not follow
the logic that's required by a coastline (see the Toronto examples,
that have been posted on this list recently, for the results).
- SWBD (SRTM Water Body) shows the state right in the moment when The
Shuttle came by and does not contain correction of tidal effects.
These tidal effects can be huge in certain areas of tidelands ... ;-)
- GSHHS should be considered to be our most accurate source of
_coastline_ data but fails significantly on certain lakes (see the
Toronto area as well).
The problem with using GSHHS for coastlines is that chances are high
that VMAP0 rivers don't end at the real coastline but instead stay
inside the 'landmass' area. This had been the reason why Curt took
'landmass' for the resent Scenery release and this is as well one
reason why we're running this Custom Scenery project: To allow people
to correct significant river mouthes to match GSHHS coastline.
This is definitely a long way to go and requires major effort but I
think there's no alternative (aside from buying commercial data).
Also there isn't 100% agreement on what is a 'lake' and what is
'ocean'. So if you use GSHHS for land/ocean and vmap0 for lakes and
rivers, you lose things like lake washington in seattle because GSHSS
thinks it's a lake, vmap0 thinks it's part of the ocean, so it gets left
out. Similar problems happen in many other parts of the world.
Curt.
--
Curtis Olson http://www.flightgear.org/~curt
HumanFIRST Program http://www.humanfirst.umn.edu/
FlightGear Project http://www.flightgear.org
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